libomp workaround for Linux, Mac

src/Simulation/Common/Simulators.Dev.props

@@ -16,6 +16,9 @@
     <QSimDll Condition="$([MSBuild]::IsOsPlatform('OSX'))">$(QsimDllMac)</QSimDll>
     <QSimDll Condition="$([MSBuild]::IsOsPlatform('Linux'))">$(QsimDllLinux)</QSimDll>
     <QSimDll Condition="$([MSBuild]::IsOsPlatform('Windows'))">$(QsimDllWindows)</QSimDll>
+    <QSimDependencies Condition="$([MSBuild]::IsOsPlatform('OSX'))">$([MSBuild]::NormalizePath($(NativeBuildPath)/../../osx))</QSimDependencies>
+    <QSimDependencies Condition="$([MSBuild]::IsOsPlatform('Linux'))">$([MSBuild]::NormalizePath($(NativeBuildPath)/../../linux))</QSimDependencies>
+    <QSimDependencies Condition="$([MSBuild]::IsOsPlatform('Windows'))">$([MSBuild]::NormalizePath($(NativeBuildPath)/../../win10))</QSimDependencies>
   </PropertyGroup>
 
   <ItemGroup>
@@ -29,6 +32,11 @@
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
       <Visible>false</Visible>
     </None>
+    <None Include="$(QSimDependencies)/**/*" >
+      <Link>%(Filename)%(Extension)</Link>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      <Visible>false</Visible>
+    </None>
   </ItemGroup>
 
   <!-- Copy the experimental simulators from xplat/qdk_sim_rs build to where we can see and use it. -->

src/Simulation/Simulators/QuantumSimulator/NativeImports.cs

@@ -14,6 +14,9 @@ public partial class QuantumSimulator
             // Preparation\Arbitrary.cs(23,41): error CS0117: 'QuantumSimulator' does not contain a definition for
             // 'QSIM_DLL_NAME' [D:\a\1\s\submodules\QuantumLibraries\Standard\src\Standard.csproj]
 
+        [DllImport("libomp", ExactSpelling = true, CallingConvention = CallingConvention.Cdecl, EntryPoint = "omp_get_num_threads")]
+        private static extern int OmpGetNumberOfThreadsNative();
+
         private delegate void IdsCallback(uint id);
         [DllImport(QSIM_DLL_NAME, ExactSpelling = true, CallingConvention = CallingConvention.Cdecl, EntryPoint = "DumpIds")]
         private static extern void sim_QubitsIdsNative(uint id, IdsCallback callback);

src/Simulation/Simulators/QuantumSimulator/QuantumSimulator.cs

@@ -28,6 +28,14 @@ public QuantumSimulator(
                randomNumberGeneratorSeed,
                disableBorrowing)
         {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                // We don't need this value, but explicitly calling an OMP function should trigger the load of libomp
+                // by .NET from the runtimes folder for the current platform, such that the later library load by the
+                // simulator does not need to know where to search for it.
+                var threadCount = OmpGetNumberOfThreadsNative();
+            }
+
             Id = InitNative();
             // Make sure that the same seed used by the built-in System.Random
             // instance is also used by the native simulator itself.